One known battery having a higher capacity and higher power than batteries for portable devices, for example, batteries for power sources for driving power tools is an assembled battery including a plurality of single cells connected through bus bars. The bus bars are secured to terminal electrodes protruding from the single cells through nuts fastened to the terminal electrodes Patent Literature 1 discloses a cell including: a lid plate having terminal-drawing through holes formed therethrough and rotation-preventing portions protruding upward from the upper surface of the lid plate; extraction electrodes having lower portions inserted through the terminal-drawing through holes into a cell container and connected to metal foils of a power generation element, the extraction electrodes being secured to the lid plate through insulating sealing members and sealed therewith; connection electrodes connected and secured to the upper portions of the extraction electrodes; and external terminals each having a base portion and a bolt portion protruding upward from the base portion, the bolt portion passing upward through a terminal through hole of one of the connection electrodes, the base portion being engaged with one of the rotation-preventing portions of the lid plate, whereby rotation of the external terminal about the axis of the bolt portion is restricted.